The House of Stuart, also spelled Stewart, was a royal house of the Kingdom of Scotland, later also of the Kingdom of England, and finally of the Kingdom of Great Britain.
The House of Stuart ruled the Kingdom of Scotland for 336 years, between 1371 and 1707. Elizabeth I of England's closest heir was King James VI of Scotland via her grandfather King Henry VII of England, who was founder of the House of Tudor dynasty. At Elizabeth's death, James Stuart ascended the thrones of the Kingdom of England and the Kingdom of Ireland and inherited the empty English claims to the French throne. From 1603, the Stuarts styled themselves "Kings/Queens of Great Britain", though there was no parliamentary union until the reign of Queen Anne, the last monarch of the House of Stuart. The Stuarts were followed by the House of Hanover, under the terms of the Act of Settlement 1701. However, a Stuart uprising spearheaded by "Bonnie Prince Charlie", grandson of the deposed James II of England, made progress in Scotland in the 1740s before being defeated by a pro-Hanover British Army.
A generation later, James' son Charles I imposed the Divine Right of Kings model upon the country. This prompted a mass migration of dissenters to the colonies, and set the stage for the eventual founding of the Federated Commonwealths of America.
Charles' role in the story is speculative, as he isn't named in the text. Based on what we know of him in OTL, and the nature of the point of divergence, he is the most likely candidate for the relevant king in the story.